This invention relates to a contact-type heat-fixing device for use in an electrophotographic copying machine in which sets of stripping pawls are provided in contacting relationship with the surface of heat roll the spacing between pawls of each set being in accordance with the size of copy papers.
Conventionally, a contact-type heat-fixing device for use in an electrophotographic copying machine is of the type, in which copy sheets having thereon toner images are passed between a heated fixing roll and a pressure roll thereby to heat-fix the aforesaid toner images on the copy sheets. However, the copy sheet is likely to stick to the fixing roll in fixing and it becomes necessary to strip the copy sheet after fixing of the fixing roll. To this end, the tip ends of stripping pawls have heretofore been held in contact with the surface of the fixing roll to forcibly strip off the copy sheet stuck or adhered to the fixing roll. The aforesaid stripping pawls are spaced at a distance from each other on the fixing roll, because if they are provided over the whole width of the fixing roll, the fixing roll is damaged or deteriorated on the surface thereof. Conventionally, a couple of stripping pawls have been provided in such a manner that they are spaced at a distance to each other in accordance with only one size of copy sheet, with the tip ends thereof being held in contact with the fixing roll. However, with such an arrangement of stripping pawls, if the size of copy paper is set at A4, it becomes difficult to strip copy sheets of B4 size, while if the size of copy paper is set at B4, it becomes difficult to strip copy sheets of A4 size, leading to some problems in the subsequent stripping operation. Thus, in order to be useful for copy papers of all sizes, it has heretofore been the practice to provide stripping pawls at an intermediate distance, therefore, one which is neither optimum for the A4, nor the B4 size copy paper. However, with copy paper of small size, such as B5 the central portion is deflected downwardly between the stripping pawls, while with copy paper which is larger in size than B5, the both end portions are deflected downwardly, thereby resulting in the cause for paper-folding.
The present invention contemplates to eliminate the aforesaid problem and has as its object the provision of a contact-type heat-fixing device wherein sets of stripping pawls are provided in a manner to be held in contact with a fixing roll wherein the spacing between pawls of different sets is in accordance with various sizes of copy papers to be stripped thereby to enable stripping copy sheets of various sizes off the fixing roll in a reliable manner.